net.automatalib.commons.util.comparison

Class CmpUtil

java.lang.Object

net.automatalib.commons.util.comparison.CmpUtil

public abstract class CmpUtil
extends Object

Various methods for dealing with the comparison of objects.

Author:

Malte Isberner

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	CmpUtil.NullOrdering Enum for controlling which rank is assigned to a null element when using a safe comparator (safeComparator(Comparator, NullOrdering)).

Method Summary

Methods

Modifier and Type	Method and Description
static <U extends Comparable<U>,T extends Iterable<U>> Comparator<T>	lexComparator() Retrieves a lexicographical comparator for the given type, which has to be an Iterable of Comparable types.
static <T extends Iterable<U>,U> Comparator<T>	lexComparator(Comparator<U> elemComp) Retrieves a lexicographical comparator for the given type.
static <U extends Comparable<? super U>> int	lexCompare(Iterable<? extends U> o1, Iterable<? extends U> o2) Lexicographically compares two Iterables, whose element types are comparable.
static <U> int	lexCompare(Iterable<? extends U> o1, Iterable<? extends U> o2, Comparator<U> elemComparator) Lexicographically compares two Iterables.
static <T extends Comparable<T>> Comparator<T>	naturalOrderingComparator() Retrieves a Comparator that compares elements according to their natural ordering (i.e., they have to implement the Comparable interface.
static <T> Comparator<T>	safeComparator(Comparator<T> baseComp, CmpUtil.NullOrdering nullOrd) Retrieves a safe comparator, which can handle null element values.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

lexCompare

public static <U> int lexCompare(Iterable<? extends U> o1,
                 Iterable<? extends U> o2,
                 Comparator<U> elemComparator)

Lexicographically compares two Iterables. Comparison of the elements is done using the specified comparator.

Parameters:

o1 - the first iterable.

o2 - the second iterable.

elemComparator - the comparator.

Returns:

< 0 iff o1 is lexicographically smaller, 0 if o1 equals o2 and > 0 otherwise.

lexCompare

public static <U extends Comparable<? super U>> int lexCompare(Iterable<? extends U> o1,
                                               Iterable<? extends U> o2)

Lexicographically compares two Iterables, whose element types are comparable.

Parameters:

o1 -

o2 -

Returns:

lexComparator

public static <T extends Iterable<U>,U> Comparator<T> lexComparator(Comparator<U> elemComp)

Retrieves a lexicographical comparator for the given type.

Parameters:

elemComp - the comparator to use for comparing the elements.

Returns:

a comparator for comparing objects of type T.

lexComparator

public static <U extends Comparable<U>,T extends Iterable<U>> Comparator<T> lexComparator()

Retrieves a lexicographical comparator for the given type, which has to be an Iterable of Comparable types.

Returns:

the lexicographical comparator.

safeComparator

public static <T> Comparator<T> safeComparator(Comparator<T> baseComp,
                               CmpUtil.NullOrdering nullOrd)

Retrieves a safe comparator, which can handle null element values. Whether null values are smaller or bigger than regular values is controlled by the CmpUtil.NullOrdering parameter.

Type Parameters:

T - original element class.

Parameters:

baseComp - the basic comparator.

nullOrd - the ordering policy for null values.

Returns:

a safe comparator using the specified underlying comparator.

naturalOrderingComparator

public static <T extends Comparable<T>> Comparator<T> naturalOrderingComparator()

Retrieves a Comparator that compares elements according to their natural ordering (i.e., they have to implement the Comparable interface. If this comparator is used on elements that don't implement this interface, this may result in a ClassCastException.

Type Parameters:

T - element class.

Returns:

the natural ordering comparator.